Computer networks are well known and are widely used in a variety of businesses. Currently, there are many different types of wired computer networks available for personal and business use, such as Ethernet, Token-Ring, Gigabit Ethernet, ATM (Asynchronous Transfer Mode), IP, with wired Ethernet being the most popular by far. The emerging Local Area Networks (LANs) are typically based on the IEEE 802.11 standard. Due to the popularity of the Ethernet network, a number of devices and methods were developed to test the Ethernet communication systems. However, as wireless computer network communication systems become less expensive to implement and maintain, they are becoming more prevalent and more widely used to communicate data among nodes of a local area network (LAN). One advantage the wireless network system has over other existing types of network communication systems is the lack of communication wire/cable. Wireless network systems allow for a large number of computer nodes to be communicated together without all of the cumbersome communication wires (such as Ethernet wires) required by non-wireless communication systems and thus provides for a more efficient use of space. Another advantage the wireless network system has over other existing types of network communication systems is that, in buildings which do not already have a wired network infrastructure, wireless systems are much easier and cheaper to implement.
However, unlike with the Ethernet network system, wireless communication networks lack sufficient means and methods for verifying performance, interoperability and compliance with the wireless standards. Although there are many reasons for the lack of testing devices and methods, development on testing devices and methods appeared to be mostly hindered by several factors, including the increased complexity of the wireless communication system as compared to the wired communication system. This increased complexity is a necessary element required to increase the reliability of the wireless system and to achieve a useful level of performance. An additional hindering factor includes the network boundaries. Unlike wired systems, wireless systems have vague network boundaries and thus, the testing of wireless networks require special considerations in order to avoid interference with other wireless systems not involved in the testing procedure. Another factor is that the communication protocols have not matured and are thus in a constant state of flux due to continued standards activity. Lastly, because many wireless equipment manufacturers began by designing and manufacturing traditional wired network systems, they typically lack an expertise with wireless equipment and thus with wireless communications issues.
As such, current methods for testing wireless communications equipment typically range from simply setting up the test in an open air environment to connecting the wireless equipment together via cables, to assembling test setups disposed within radio frequency (“RF”) shielded rooms. Although open air test setups have the advantage of being simple to construct, they typically suffer from a variety of problems. First, the open air environment is difficult to control. It is not possible to precisely control signal levels and test topologies in order to verify protocol implementation. Often, due to intermittent interference, specific tests cannot be repeated with consistent results. Second, each test system takes up at least one radio channel and because radio channels are regulated and allotted by the government they are a scarce resource. Thus, an active test lab may use all of the allotted channels for one test setup thereby preventing multiple independent test setups from operating simultaneous and preventing multiple engineers or production workers from working side by side. However, one way to overcome the limitations of the open air test setup is by connecting the test setup to wireless equipment through an RF cable system having RF cables, RF combiners and RF attenuators. Using this approach, transmitter signals can be communicated to the wireless system receivers via the RF cable system. Not only does this allow the signal power levels to be controlled using RF attenuators, but the setup can support flexible network topologies in a controlled environment under repeatable test conditions.
While this may be an improvement over the open air test setup, interference issues are still present. One of these interference issues involves the ability to set up a test system in a small area while allowing other test systems to operate nearby, such as on an adjacent test bench. Unfortunately, because a great number of wireless systems have extremely sensitive receivers in order to operate over a useful range of distances between transmitter and receiver, this is impractical. Flexible cables that are used for these test setups do not provide a sufficient level of RF isolation to allow for more than one interference-free test setup in the same lab. Thus, if multiple test setups are used, signals from the transmitters of one test setup can leak from the cables and infiltrate the receivers of the other test setups, greatly degrading the reliability and validity of the test results.
Although RF shielded rooms can provide for an isolated environment, these rooms are expensive to build and maintain and typically require a substantial amount of space. Additionally, the problem of running multiple test setups in the same shielded room remain because although the shielded room isolates the test setup from RF interference sources located outside of the shielded room, it does not isolate the test setup from RF interference sources within the shield room. Moreover, because of the expense of the shielded rooms, they are typically shared among many engineers who may have different needs for the room. Thus, because assembling and disassembling a test setup may range from many hours to several days, there is an incentive to not change the test setup very often, thus limiting the productivity of the test organization. Furthermore, an additional cost of testing wireless systems includes the purchase of specialized equipment for performing, coordinating, automating and synchronizing the tests. The current art requires that the test system be assembled from commodity components and because these components were most likely not designed to solve the whole problem, the components typically must be integrated into a working system. Once the test system has been assembled, test software typically must be developed in order to automate the testing process and, depending on the complexity of the test setup, a significant effort may be needed to develop the control software. This takes additional time, effort, expertise and represents a significant labor cost.
Moreover, unless tight regulations are developed and maintained, each test setup will be different and because each setup was constructed from components not specifically suited to the job, each component of the test setup can have its own method of programming. As a result of this lack of basic integration, it is very difficult to arrange tests that require coordination of RF transmissions. This whole effort is typically very expensive, time consuming and inefficient for the wireless equipment manufacturers. Moreover, the cost of this setup is further exacerbated by the cost of equipment integration, calibration and customized test software development. Tests that involve overlapping BSSs (Basic Service Sets), roaming and hidden stations are difficult to set up and perform because they typically require flexible control over wireless network topology thus requiring wireless stations and access points to be carried around or wheeled on carts.
Thus, there is a need for a test system that provides a flexible cabled environment for RF testing, wherein the flexible cabled environment allows for flexible topological configurations and wherein the test environment provides a shielded test platform which will allow for close proximity testing of different wireless systems without interference.